Uncertainty about the size of the penalty that Deutsche Bank faces from the US authorities for a mis-selling scandal a decade ago has knocked almost 4% off the share price of Germany’s biggest bank.

The shares fell on Monday after a frenzy of speculation that John Cryan, chief executive of Deutsche Bank, would secure a deal with the US Department of Justice while at last week’s meeting of the International Monetary Fund in Washington.

But a report in Germany’s largest newspaper, Bild am Sonntag, that Cryan had failed to secure a settlement with the DoJ over the sale of residential mortgage backed securities (RMBS) between 2005 and 2007 hit sentiment as the German stock market opened for trading.

While Deutsche Bank has been under pressure on the stock market since the start of the year, the admission that the DoJ had suggested a $14bn (£10.5bn) penalty for the RMBS scandal has caused the latest nosedive in its shares.

Deutsche Bank has described it as an “opening position” and insisted it will not pay that sum. Cryan, a Briton who has been running the bank since last year, has also been forced to insist that he has not asked for German government’s help.

News agency Agence France-Presse had suggested the bank might be able to settle with the DoJ for $5.4bn.

Cryan has tried in the recent weeks to reassure the 100,000 staff, including about 9,000 in the UK. “Our bank has become subject to speculation. Ongoing rumours are causing significant swings in our stock price. It is our task now to prevent distorted perception from further interrupting our daily business,” he has said.